Rotating stall is a phenomenon that can lead to mechanical stresses and damage within an axial-flow machine, such as a compressor of a gas turbine. During the startup of a turbine, rotating stall can occur in a compressor due to compressor operation outside of the standard operating conditions for the compressor. Flow separation from the blades may often persist over a wide range of speeds within the compressor. In certain circumstances, a frequency associated with the rotating stall may be similar to a natural resonant frequency of the compressor blades, thereby leading to resonance, relatively high mechanical stresses, and a greater risk of damage within the compressor.
In conventional turbine control systems, a startup sequence typically involves providing a relatively large gas flow to a compressor while simultaneously providing a relatively large fuel flow to a combustor of the turbine. In other words, these conventional systems attempt to bring the turbine to a steady state operating condition by maximizing the air flow to a compressor and the fuel flow to a combustor. However, as mentioned above, these conventional systems can lead to operation outside of the standard operating conditions for the compressor and, mechanical stresses due to rotating stall. Accordingly, improved systems and methods for controlling the startup of a gas turbine are desirable.